Pontine reticular formation and vestibular nucleus neurons display many of the same complex discharge patterns associated with various types of eye movements. The patterns include units which exhibit high-frequency bursts of activity that precede saccades and quick-phase eye movements of rotatory vestibular nystagmus, units which discharge tonically during fixation and are modulated during visual smooth pursuit and vestibular slow-phase movements, units that pause during both saccades and quick-phase movements, and units that closely resemble oculomotor neurons in displaying both a burst during rapid eye movements and tonic, eye-position correlated activity during fixation. The quantitative behaviro of units in these two brain-stem complexes are being studied in alert monkeys conditioned to fixate a movable target display. Particular attention is being focused on the similarity and differences in discharge characteristics during rotationally induced and visually guided movements in an effort to answer the question of where in the supranuclear structure of the oculomotor system the inputs from these two drives are integrated. In addition, the possibility of shared neural substrates that perform similar functional roles required by both the vestibular and visual subsystems is considered.